Q.70 In the Polyacrylamide Gel Electrophoresis, what is the role of APS (ammonium
persulphate)?
1. It is an alkylating agent that is used with TEMED to catalyze the
polymerization of acrylamide and bisacrylamide
2. It is an reducing agent that is used with TEMED to catalyze the
polymerization of acrylamide and bisacrylamide
3. It is an oxidizing agent that is used with TEMED to catalyze the
polymerization of acrylamide and bisacrylamide
4. It is an mutagenic agent that is used with TEMED to catalyze the
polymerization of acrylamide and bisacrylamide
Role of APS in Polyacrylamide Gel Electrophoresis
Ammonium persulfate (APS) plays a key role in PAGE gel preparation by initiating polymerization. The correct answer is option 3.
Correct Answer
3. It is an oxidizing agent that is used with TEMED to catalyze the polymerization of acrylamide and bisacrylamide
APS decomposes to generate sulfate free radicals, acting as an oxidizing agent, which starts the polymerization reaction. TEMED accelerates this process by catalyzing APS breakdown in the gel mixture.
Option Analysis
| Option | Description | Correct/Incorrect | Explanation |
|---|---|---|---|
| 1 | Alkylating agent with TEMED for polymerization | Incorrect | APS does not alkylate; it oxidizes to form radicals, not covalent alkyl bonds. |
| 2 | Reducing agent with TEMED for polymerization | Incorrect | APS is oxidizing, not reducing; reducers like DTT prevent oxidation elsewhere. |
| 3 | Oxidizing agent with TEMED for polymerization | Correct | Matches APS function: generates free radicals via oxidation for acrylamide-bisacrylamide chaining. |
| 4 | Mutagenic agent with TEMED for polymerization | Incorrect | APS is not primarily mutagenic; any risk is secondary to its initiator role. |
Polymerization Mechanism
APS (chemical formula (NH4)2S2O8) breaks down into SO4- − radicals with TEMED. These radicals attack acrylamide monomers, forming chains cross-linked by bisacrylamide for the porous gel matrix used in electrophoresis.
Exam Preparation Tips
Focus on APS as the initiator (oxidizing) and TEMED as the catalyst for NEET/CSIR/IFS biology MCQs. Practice gel recipes: 10% APS stock is common.
